Send touch events to root pipeline, and allow forwarding to iframes.

[glennw]

Instead of letting the compositor try to find the correct scroll
layer for a touch event, switch touch events to work the same way
that mouse events do.

Touch events are now dispatched to the root pipeline, and then
forwarded to child iframes as required.

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This change is

[highfive]

Heads up! This PR modifies the following files:

• @asajeffrey: components/constellation/constellation.rs
• @KiChjang: components/script/script_thread.rs, components/script/dom/document.rs, components/script_traits/script_msg.rs, components/script_traits/script_msg.rs

[highfive]

Warning

• These commits modify script code, but no tests are modified. Please consider adding a test!

[glennw]

r? @mbrubeck

This contains the event forwarding for touch events we discussed on IRC. See #8811 for details.

I've tested this on my (Linux) touchscreen laptop and as far as I can tell it's all working as previously. I've tested touch events, and touch scrolling on normal pages, and also within iframes (via browser.html).

[bors-servo]

☔ The latest upstream changes (presumably #13596) made this pull request unmergeable. Please resolve the merge conflicts.

[mbrubeck]

-S-awaiting-review +S-needs-code-changes

r=mbrubeck with a minor nit fixed:

---

Reviewed 4 of 5 files at r1.
Review status: 4 of 5 files reviewed at latest revision, 5 unresolved discussions, some commit checks failed.

---

components/compositing/compositor.rs, line 1534 at r1 (raw file):

        self.send_event_to_root_pipeline(TouchEvent(TouchEventType::Down,
                                                    identifier,
                                                    translated_point.to_untyped()));

Nit: .to_untyped() is not needed here, because translated_point is already "untyped."

---

components/compositing/compositor.rs, line 1561 at r1 (raw file):

                self.send_event_to_root_pipeline(TouchEvent(TouchEventType::Move,
                                                            identifier,
                                                            translated_point.to_untyped()));

.to_untyped() not needed.

---

components/compositing/compositor.rs, line 1572 at r1 (raw file):

        self.send_event_to_root_pipeline(TouchEvent(TouchEventType::Up,
                                                    identifier,
                                                    translated_point.to_untyped()));

.to_untyped() not needed.

---

components/compositing/compositor.rs, line 1585 at r1 (raw file):

        self.send_event_to_root_pipeline(TouchEvent(TouchEventType::Cancel,
                                                    identifier,
                                                    translated_point.to_untyped()));

.to_untyped() not needed.

---

components/compositing/compositor.rs, line 1595 at r1 (raw file):

            let dppx = self.page_zoom * self.device_pixels_per_screen_px();
            let translated_point = (point / dppx).to_untyped();
            self.send_event_to_root_pipeline(TouchpadPressureEvent(translated_point.to_untyped(),

.to_untyped() not needed.

---

Comments from Reviewable

[glennw]

Addressed comments and rebased.

[mbrubeck]

@bors-servo r+

---

Reviewed 1 of 5 files at r1, 3 of 3 files at r2.
Review status: all files reviewed at latest revision, all discussions resolved.

---

Comments from Reviewable

[bors-servo]

📌 Commit 291af9d has been approved by mbrubeck

[bors-servo]

⌛ Testing commit 291af9d with merge 9d3fc76...

[bors-servo]

☀️ Test successful - arm32, arm64, linux-dev, linux-rel-css, linux-rel-wpt, mac-dev-unit, mac-rel-css, mac-rel-wpt1, mac-rel-wpt2, windows-dev